Electrical network



-E.,L. NORTON ELECTRICAL NETWORK Filed March 31. 1926 pril 3, 1928.

, Patented Apr. 3, 1928.

UNiTED STATES PATENT oFFIcE. l

EDWARD L. NORTON, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COM- IPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

i ELECTRICAL NETWORK.

Application led March 31, 1926. Serial No. 98,649.

This invention relates to electrical. n etworks and"partici1larly to transmission equalizing networks of the type known as constant resistance networks and has for 5 an object to improve such networks.

' U. S. Patent No. 1,603,305, issued October 19, 1926, to O. J Zobel, describesvarious forms of constant resistance equalizing networks and gives a discussion of the general properties of this type and the method of its lapplication to the equalization of attenuation in transmission systems. l

A articular object of this invention is to re uce the number of impedance elements '35 required for the construction of a constant resistance network having a characteristic which provides a specified attenuation correction.

A further object of the invention is to provide a constant resistance network which may be connected between two terminating circuits having dierent impedances.

In general this inventionv consists of a constant resistance transmission correcting network comprising a bridged T arrangement of elements in which the two series arms of the bridged T are not alike. Howl ever, the particular characteristics of the networks of this inventiony can -be -best understood by reference to the following detailed description in connection with the drawing in which: Figs. 1, 3, 5 and 6 show generalized impedance diagrams of the networks of this invention, Figs. 2` 4 and 7 equivalent networks of the Zohel type and Figs. 8 and 9 specific examples ot the networks of this invention.

This invention in its general form may be represented by the two generalized impedance structures shown in Figs. 1 and 3. The networks ot Figs. 5 and 6 are identical with Figs. 1 and 3, respectively except that different points are used .for terminals.

The form of the invention shown in Fig. l comprises a network connected lbetween the two sets of terminals 1, 2 and, 3, 4. T he resistance connected to the terminals 3, 4 represents a load circuit having a constant resistance impedance, R1. The network consists of two impedances cZ, +aZ2 and Z, connected in series between the terminals 1 and 3, a resistance R bridge across 'these imtype network having unequal series arms (as v in the form shown in Fig. 1), Z2 Aand Z1 bridged by an impedance bZ, andl a shunt arm of resistance R connected to the junction of Z2 and Z1.

By elementary analysis lbased on Kirchhoff s laws it can be shown that these networks have a constant resistance impedance It at their terminals 1, 2 and 7, 8, respectively when: i

or, (for Fig. 2)

In designing networks of this type it is: most convenient to refer to the equivalent network of the series-shunt type, formula: for the design of which together with examples are given in the patent to Zobel rcferred to above. Reference is also made to Chapter XVIII of Transmission Circuits for Telephone Communication by K. S. Johnson, Van Nostrand and Company.

Fig. 2 shows a full series terminated network of the type described by Zobel which has a transmission characteristic equivalent to that of the network of Fig. 1. Fig. 4 shows a full shunt terminated network having a transmission characteristic equivalent to the network of Fig. 3. The networks of in which by detinitio'nz` Figs. 2 and 4 are of the tVDes shown in Figs.

B= @c+ las,

Z2. C"1+b and a The transmission loss in transmission units,

caused by these structures is,

yTU 20 log, 1

The transmission loss caused by the networks of Figs. 1 and 2 is equal to this plus a constant loss equal to the relection loss between the input resistance and the terminating resistance thus:

land for Fig. 2

The networks of this linvention may also be used for operating between an input resistance and a load resistance which are equal as shown in Figs. 5 and.

The network of Fig. 5 is identical with that of Fig. 1 except that a load circuit of constant impedance R is connected to the terminals 5, 6 whereas in Fig. 1 a load circuit of constant im edance R1 is connected to terminals v3, 4. v imilarly the network of Fig. 6 is identical with that of Fig. 3 except that a load of constant impedance R is connected to the terminals 11, 12 in place of a load circuit of constant impedance R2 connected to the terminals 9, 10.

The networks of these two figures have Z transmission characteristics equal to that of the equivalent bridge network of the -type shown in Fig. 5 of the Zobel patent and Fig. 1E of the chapter of the K. S. Johnson book referred to above. The equivalent network is composed of series arms Zn comprising two impedances C and D and a resistance Ri in parallel and shunt arms Z2, comprisfand for the equivalent of Fig. '5.,

pedane-e element connecteddirectly betweenw ing two impedances A and B and a resistance R connected 1n serles, 1n whlch:

' 75 soy The transmissionloss, in transmission units, 85.

caused by this structure is:`

`or. for Fig. 6.

The networksof Figs. 5 and. 6 can be seen to require considerably fewer elements y than is required for the networkof Fig.}7. v l* Thus by the use of this invention it is `possible to obtain at a considerable saving in elements the same transmission characteristicas is obtained with the bridge type networkofFigT. I l

Figs. 8 and 9 show specific examples of the circuits of type of Figs. 1, 5 and 2, 6 respectively in which Z1 is a, condenser of capacity C andZe a coil of, inductance L. These circuits, of course, only show particu` lar embodiments ofthe invention. and any combination of elements which will give the y transmission characteristic desired may be used for the generalized impcdances Zl and What is claimed is: p A wave transmission' network having a pair of -jinput terminals and a pair of `output terminals adapted to be connected to a load circuithaving a substantially constant resistance `impedance overaringe ofl re-. quencies, said network com rising an im an input terminal and an output terminal,

a pair of unequal impedance elements having a common terminal and having their other terminals connected respectively to the 5 terminals of said first impedance element, and a fourth impedance element having one terminal connected to said common terminal and having connections from its other terminal to the remaining input and output ter- 10 1nina1s,'the impedances of the elements of said network being so proportioned with respect to one .another and to the impedance of the load circuit that the'input impedance of said network is a constant resistance over said range of frequencies.

In Witness whereof, I hereunto subscribe my name this 29th clay of March A. D.,

EDWARD L. NORTON. 

